The present invention relates to electrochemical means for producing heat and/or hydrogen gas, and more particularly to a simple, reliable, efficient and compact means for producing heat and/or hydrogen gas for use in remote areas. For example: the present invention may be used for replacing lost body heat for undersea divers or combat troops; it can be used for heating machinery or instruments in remote or cold areas; it may also be used for production of electrical or mechanical energy through use of a heat or expansion engine in remote locations; and, hydrogen produced thereby can be used for buoyancy in deep sea recovery operations or for production of energy by use of fuel cell type systems.
The electrochemical reaction between active metals such as magnesium and passive metals such as iron when immersed in electrolyte has been proposed for use as a heat source. Other systems advocate the use of massive plates of magnesium and iron (two-plate system) separated by an electrode gap, electrically shorted together and immersed in seawater. Such arrangement results in complex control problems and requires the use of large plate surface areas which result in bulky cumbersome apparatus. The arrangement is not adaptable to direct production of localized heat, thus the diver must carry a single bulky reaction chamber which can greatly restrict his maneuverability and reduce his effectiveness. In the two-plate system, heat production effectiveness is reduced because of operational problems associated with disposal of reaction products, magnesium hydroxide and hydrogen gas. Volumes of hydrogen produced requires large gas collection area to prevent dewatering of heat producing plates. Removal of hydrogen from the reaction chamber is complicated because of changing orientation of diver. Production of magnesium hydroxide tends to clog reaction area between plates, thus reducing power output. Reaction control is difficult and complicated because of continual depletion of active metal and the subsequent increasing electrode gap.
Previous methods used to produce hydrogen gas for deep sea buoyancy operations use exotic, expensive and hazardous chemicals which are recently becoming unavailable. For example, the use of hydrazine is presently being developed. Hydrazine requires complex control systems for ocean operations. Hydrazine is toxic, a moderate fire hazard and potentially explosive.
Past proposals for the use of metallic elements for generation of hydrogen for buoyancy have been neglected because of the relatively slow reaction rate of metals with seawater. Coupling active metals with a passive metal increases this rate over 100 fold. By the use of the micro electrochemical cells described herein, another order of magnitude increase in reaction rate can be achieved for use in generating hydrogen.